Deployment of medical devices such as implants usually requires accurate and reliable placement at a specific site within the vasculature of a patient. For example, an abnormal bulge or aneurysm that may occur in a patient's vessel can be treated by deploying one or more embolic coils into the bulge or aneurysm to occlude the flow of blood into it.
Many different systems and methods have been proposed for delivering such implants, or indeed other medical devices, and most of these involve delivery of the device to the selected site via a catheter and subsequent release or detachment of the implant at the selected site. Some systems, for example, have a mechanism with gripper arms that grip an appropriate feature of the implant (such as enlarged head portion). When the implant is positioned at the selected site, the gripper arms are opened to release it. To ensure effective deployment of the implant once in situ, the gripper arms may be biased open and are therefore constrained into the gripping position during deployment until the implant reaches the desired position. Whilst the prior art systems are generally effective, problems have occurred due to the design of such release mechanisms, particularly in systems where the release mechanism is biased into an open position. In some cases the implant has been released prematurely. This is clearly undesirable as the implant will be incorrectly positioned and must be removed, thus disrupting the medical procedure and potentially risking the health of the patient.
Accordingly there remains a need for an improved release mechanism for releasing a medical device, particularly an implant, at a selected site within the vasculature of a patient, which is reliable and resistant to premature release of the device.